Graphite continuous casting mold



1967 T. J. MARCHLIK GRAPHITE CONTINUOUS CASTING MOLD 2 Sheets-Sheet 1 Filed June 18, 1964 INVENTOI? THADDEUS J. MARC/ LIX Feb. 21, 1967 T. J. MARCHLIK 3,304,585

GRAPHITE CONTINUOUS CASTING MOLD Filed June 18, 1964 2 Sheets-Sheet z INVE/V 70/? 7775400505 J. MARC/ LIX ATTORNEYS.

Patented Feb. 21, 1967 3,304,585 GRAPHITE CONTINUOUS CASTING MOLD Thaddeus J. Marchlilr, Camden, N.J., assignor, by mesne assignments, to Ascast Corporation, Riverton, N.J., a corporation of New Jersey Filed June 18, 1964, Ser. No. 376,006 4 Claims. (Cl. 22--57.2)

This invention relates to an improved apparatus and method for producing cast metals, such as copper, copper base alloys, aluminum, aluminum alloys, and the like.

In the production of cast metals, it is common practice to pour molten metal through a die or mold. A portion of the mold is cooled. As the molten metal reaches the cooled portion of the mold, the metal solidifies, and the casting which is formed is withdrawn from the bottom of the mold.

The selection of the mold material used in the casting process is extremely important. The mold material must have a high heat conductivity so that heat may be withdrawn from the molten metal through the mold in as rapid a fashion as possible.

The mold material should have a lubricating action on the cast metal as it flows through it. This will not only effect a rapid transfer of the cast metal through the mold, but will decrease the probability of surface defects forming in the cast metal. The friction between the metal and the mold walls tends to cause fracturing of the newly solidified metal.

Another important factor in selecting a suitable mold material is its ready machinability. The mold, in certain instances, must be machined so as to be employed in different type casting machines.

It has been found that graphite fulfills the above requirements.

A good casting mold should also be formed with a heat sink above the solidifying zone of the molten metal. .The heat sink will allow a pool of fluid to be maintainedon the solidifying metal beneath it so that the pool will readily feed the shrinking metal below it to prevent shrinkage defects. Further, since crystallization takes place from a comparatively small volume of molten metal, segregation will not take place. The pool of metal will prevent or relieve all shrinkage stresses.

While graphite has the above noted advantages for use as a casting mold, it has the inherent disadvantage of i excessive heat transfer through the mold walls at any given time.

Prior processes and apparatus use steel or copper cooling jackets around the mold walls to produce the necessary heat transfer to solidify the molten metal flowing through the mold. The heat transferred to the coolant has to pass not only through the mold walls but through the jacket Walls. Direct cooling of the mold walls Was not considered feasible since the graphite was to porous. The coolant could penetrate it, enter the molten metal, and possibly cause an explosion. This double heat transfer of necessity limits the casting rate.

This invention relates to a casting apparatus and method for metals which employs a graphite mold of such low porosity that direct cooling of the mold is feasible.

Accordingly, it is an object of this invention to disclose a method and apparatus for casting metals at relatively high casting rates or speeds.

A further object of the present invention is to provide an apparatus and method for casting metals which employs a graphite mold which is directly cooled by a coolant whereby its heat transfer characteristics are greatly improved.

A still further object of this invention is to disclose an apparatus and method for casting metals which employs a graphite mold which is substantially impervious to a coolant fluid.

Yet another object of this invention is to provide an apparatus and method for casting metals which employs a graphite mold having a heat sink so as to prevent shrinkage defects in the solidifying molten metal flowing through the mold.

Another object of this invention is to disclose an apparatus and method for casting metals which employs a graphite mold directly cooled by a coolant and a heat sink above the direct cooling zone so that if any coolant does penetrate the graphite mold, it will enter the mold below where the metal has solidified and evaporate, thereby increasing the cooling effect.

Other objects will appear from the disclosure which follows hereinafter.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a fragmentary sectional view through a continuous casting machine illustrating as a component thereof-a directly cooled mold used in the continuous casting of metals by said machine.

FIGURE 2 is a cross-sectional view taken substantially along the plane indicated by the line 2 -2 of FIGURE 1.

FIGURE 3 is a fragmentary sectional view through a discontinuous casting machine illustrating another embodiment of a directly cooled mold as a component thereof for use inthe discontinuous casting of metals by said machine.

FIGURE 4 is a cross-sectionalview taken substantially along the plane indicated by the line 4-4 of FIGURE 3.

Referring now to the drawings in detail, wherein like elements are designated by like numerals, FIGURES 1 and 2 illustrate apparatus for continuously casting metals which is generally designated by the numeral 10.

The apparatus 10 includes a molten metal receptacle 12 formed from refractory material. Molten metal 14 is poured from a suitable source into the receptacle 12. The molten metal 14 flows from the receptacle 12 through a mold 18 positioned in an opening 16 in the side of the receptacle. The molten metal 14 solidifies in the mold 18 as shown at 20. The solidified cast metal 20 is disposed between rollers 22 and 24 which continuously withdrawsit from the mold 18.

The mold 18 includes an annular chamber 26 surrounding the bore in the mold through which the molten metal flows. A coolant, such as water 28, is fed to the annular chamber 26 by means of an inlet conduit 30. The water 28 continuously circulates in the annular chamber 26 and is Withdrawn through an outlet conduit 32.

The mold 18 is formed from graphite having a fluid permeability of 1 to millidarcys. A darcy is defined as the flow of a cubiccentimeter per second per square centimeter per atmosphere per centimeter for a gas of one centipoise viscosity. Hence, it will be understood that the graphite mold 18 is substantially impervious to the coolant 28 within the chamber 26. Hence, there is little chance of any water penetrating the mold walls and mixing with the molten metal flowing through the mold bore. I

Due to the fact that the coolant 28 directly contacts the molding surface surrounding the flowing molten metal, the solidified metal casting 20 is produced at a high casting rate or speed. Heat is withdrawn from the molten metal through the mold surface surrounding the bore in the mold and passed directly to the coolant 28. The withdrawn heat need not be passed through an additional surface as has previously been proposed. The direct cooling of the mold effects a greater heat transfer rate thereby allowing for faster solidification of the molten metal, as well as preventing localization of the heat in the graphite mold which will have the tendency to burn away portions of the graphite mold.

The mold 18 is also provided with a heat sink portion 31. The heat sink 31 is upstream from the coolant chamber 26. Hence, a pool of molten metal is maintained in the mold above the solidified casting 20. The pool of metal will readily feed the shrinking metal downstream from it to prevent shrinkage effects in the casting. The presence of the pool of metal prevents and relieves all shrinkage stresses. Further, even if some coolant should penetrate the mold, the coolant will not enter the mold in the region of the liquid metal, but rather where the metal has solidified. This moisture, will evaporate, and in so doing, will increase the cooling effect. The heat sink is used from ten percent to sixty percent of the mold length depending on the metal to be cast.

As previously pointed out, it is desirable that the graphite mold have as low a permeability as possible and preferably in the range of 1 to 100 millidarcys. This will, for all practical purposes, preclude the possibility of the coolant entering the molten metal prior to its solidification. One possible method of producing a graphite mold whose permeability is in the range of one to one hundred millidarcys is fully disclosed in Patent 2,972,- 552 of L. L. Winter.

The mold 18 is also preferably slotted, as shown at 36. The slots 36 permit contraction of the bore surrounding the solidified casting 20. This will permit the mold 18 to maintain intimate thermal contact with the casting 20.

Referring now to FIGURES 3 and 4, a discontinuous type of casting apparatus is generally designated by the numeral 40. The casting apparatus 40 includes a molten metal receptacle 42 adapted to house a pool of molten metal 44. The molten metal receptacle 42 includes a plug 45 having passages 47 for dispensing molten metal through a bore formed in a graphite mold 46. The molten metal 44 solidifies in the mold 46 as shown at 48 and is withdrawn through the bottom of the mold by a vertically reciprocable pedestal assembly generally designated by the numeral 50. When the pedestal assembly 50 reaches the lower limit of its reciprocable stroke, the casting operation will have been completed.

The graphite mold 46 is supported in a conventional manner by the apparatus 40 below the plug 45. An annular coolant spray tube 54 is provided in surrounding 'relation to the downstream end of the mold 46. The

spray tube 54 is supported by the apparatus 40 in a conventional manner in the aforementioned position.

The spray tube 54 includes a plurality of coolant apertures 58 for directing a spray of coolant against the cylindrical surface of the mold 46. A coolant such as water is fed to an inlet conduit 60 communicating with the interior of the spray tube 54.

Welded to the outer periphery of the spray tube 54 is a conical spray shield 56. The shield 56 protects the various components of the apparatus from the coolant spray emitted from the tube 54 and directs the spray to an accumulation tray (not shown).

The mold 46 is formed from graphite having a fluid permeability of 1 to millidarcys. It is provided with a heat sink portion 52 above the spray tube 54 for the same purposes as the heat sink 31 of the mold 18. The mold 46 is also slotted as shown at 62 for the same purpose as the slots 36 in the mold 18.

It will thus be apparent that as the molten metal flows through the bore in the graphite mold 46, it will solidify by having heat withdrawn from it through the walls of the mold. The mold walls surrounding the bore through which the molten metal passes is cooled by the coolant spray emitted through the passages 58 in the spray tube 54. Since the mold walls are directly cooled, a faster rate of heat transfer will occur.

It should also be understood that the mold 46 can be used with a continuous casting machine and the mold 18 with a discontinuous casting machine, if desired.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specifications as indicating the scope of the invention.

Iclairn:

1. Apparatus for casting metals comprising a graphite mold having a bore therethrough adapted to receive a stream of molten metal, said bore having an upstream portion and downstream portion, said graphite mold comprising a material having a fluid permeability of 1 to 100 millidarcys, mold cooling means adjacent the downstream portion of said bore for solidifying molten metal flowing through the downstream portion of said bore, a portion of said mold defining a heat sink adjacent the upstream portion of said bore for maintaining metal in said upstream portion in the molten condition, said heat sink extending between 10 and 60% of the overall mold length, said downstream mold cooling means including means for applying a fiuid coolant directly to a surface of said mold, said surface surrounding the downstream portion of said bore and being spaced from said bore by a wall of said graphite material.

2. Apparatus in accordance with claim 1 wherein said mold cooling means includes an annular fluid spray tube surrounding said mold surface, a plurality of spaced coolant passages in said spray tube, a conical shield projecting downwardly from said spray tube and about said mold, and a coolant inlet conduit communicating with said spray tube.

3. Apparatus in accordance with claim 1 wherein said mold cooling means includes an annular chamber in said mold surrounding the downstream portion of said bore.

4. Apparatus in accordance with claim 1 wherein said means includes an annular fluid spray tube adjacent the downstream portion of said bore.

References Cited by the Examiner UNITED STATES PATENTS 2,543,936 3/1951 Reynolds 2257.2 2,618,032 11/1952 Traekner. 3,076,241 2/ 1963 Simonson et al. 2257.2 X

FOREIGN PATENTS 925,940 5/ 1963 Great Britain.

1. SPENCER OVERHOLSER, Primary Examiner,

R. S. ANNEAR, Assistant Examiner, 

1. APPARATUS FOR CASTING METALS COMPRISING A GRAPHITE MOLD HAVING A BORE THERETHROUGH ADAPATED TO RECEIVE A STREAM OF MOLTEN METAL, SAID BORE HAIVNG AN UPSTREAM PORTION AND DOWNSTREAM PORTION, SAID GRAPHITE MOLD COMPRISING A MATERIAL HAVING A FLUID PERMEABILITY OF 1 TO 100 